A chemical container employed for automatic liquid chemical transmission, such as a container for storing the flowing liquid for high performance liquid chromatography (HPLC), typically includes a body portion and a cap portion, with the cap portion having a plurality of channels. A pipeline for transmitting the liquid chemical would pass through one of the channels of the cap portion and enter the container, with one end of the pipeline positioned close to the bottom of the container on the inside of the container, and the other end of the pipeline connected with an inlet of a liquid pump located outside the container. The liquid chemical in the container is then transmitted to a destination outside the container by a force of suction generated by the liquid pump. In order to ensure a stable transmission speed of the liquid chemical, gas nitrogen is usually employed which is pumped into the container through another channel of the cap portion. The nitrogen produces a low level pressure at the surface of the liquid chemical inside the container, thereby ensuring a sufficient supply of the liquid chemical at the inlet of the liquid pump.
In the field of semiconductor manufacturing, a variety of liquid chemicals are often used to realize various processing steps of cleaning, etching or otherwise treating a surface of a semiconductor substrate. For high-end semiconductor products, these processing steps require an utmost cleanliness of the substrate surface. Therefore, any possible pollution to the liquid chemicals during the preparation and transmission thereof, as well as relevant safety issues, are to be avoided. For this purpose, a fully automatic control system is necessary to realize an end-to-end process of a liquid chemical, ranging from the preparation and transmission to the after-use collection of the chemical. Consequently, chemical containers that are specially made are needed to handle the liquid chemical fully automatically.
Chemical containers used in semiconductor manufacturing are required to be corrosion resistant and would not affect the purity and the ultra-cleanliness of the liquid chemicals liquids contained therein. In semiconductor manufacturing, chemical recipes containing hydrofluoric acid are often used, and the concentration of metal pollution in the liquid chemical (i.e., the hydrofluoric acid) is required to be lower than one part per billion (ppb). Therefore, a chemical container for this purpose is usually made of ultra-pure, corrosion-resistant plastic materials, such as polypropylene (PP), polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), polyvinylidene difluoride (PVDF), and the like. A plastic container available on the market typically has one of the following two structures: either a structure consisting of a body portion and a cap portion that has a plurality of channels, or an integral structure having the body and the cap portions integrated in one piece.
In order to reduce particle pollution to a liquid chemical, one may choose to use liquid pumps as little as possible in the transmission of the liquid chemical. Instead, the liquid chemical may be transmitted by inputting nitrogen into a chemical container containing the liquid chemical. The nitrogen would produce a pressure in the chemical container and thereby pressing the liquid chemical out of the chemical container. This process, however, may cause gas leakage (i.e., leakage of the nitrogen) for the type of containers that have separate body portion and cap portion. The gas leakage may happen at the connection between the body portion and the cap portion when the pressure caused by the nitrogen inside the chemical container reaches 10 psi or so. This is because a container of this type (i.e., a container having separate body portion and cap portion) is usually quite limited in terms of the inner pressure it can bear. This not only limits a highest possible pressure level the inner pressure of the container can be raised to, but also causes safety concerns regarding vapor of the liquid chemical that is brought out by the leaking gas (i.e., nitrogen). On the contrary, an integral container with the body and the cap portions integrated in one piece would not suffer from the problem of gas leakage. However, the cost of manufacturing the integral container is very high, as a special mold is usually needed for the manufacturing.
Accordingly, it is necessary to provide an improved solution to the problems described above.